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Phosphine-Based Dinuclear Platinum(II) Diamido, Amido−Hydroxo, Oxo−Amido, Oxo−Imido, Diimido, and Dihydrazido Complexes1

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posted on 11.03.1999, 00:00 by Jian Jun Li, Wei Li, Alan J. James, Todd Holbert, Tristan P. Sharp, Paul R. Sharp
The platinum(II) amido−hydroxo and diamido complexes [(L2Pt)2(μ-NHR)(μ-OH)](BF4)2 (1) (L = PPh3, R = Ph, p-tol, p-ButC6H4, p-NO2C6H4; L2 = dppp, R = Ph, p-tol) and [L2Pt(μ-NHR)]2(BF4)2 (2) (L2 = dppm, R = H, Ph, p-tol, NH2; L2 = dppe, R = H, Ph, p-tol; L2 = dppp, R = H, NH2; L2 = dppb, R = NH2; L = PMe2Ph, R = H) are prepared from the reaction of [L2Pt(μ-OH)]2(BF4)2 with NH2R. [(PPh3)4Pt2(μ-OH)(μ-NHR)](OTf)2 (R = p-NO2C6H4) (1a), the triflate analogue of 1 (L = PPh3, R = p-NO2C6H4), is similarly prepared from [L2Pt(OH2)2](OTf)2. Crystals of 1·CH2Cl2 (L = PPh3, R = p-tol) from CH2Cl2/ether are monoclinic (P21/n) with a = 16.331(5) Å, b = 23.908(5) Å, c = 19.233(6) Å, β = 99.01(1)°, and Z = 4. The cationic portion consists of two edge-shared square-planar Pt centers folded at the edge with cis-phosphines and bridging hydroxo and amido groups. LiN(SiMe3)2, LiNPri2, LiPh, or LiMe addition to 1 (L = PPh3, R = Ph, p-tol, p-ButC6H4) or 1a deprotonates the hydroxo group, forming the amido−oxo complexes [(L2Pt)2(μ-NHR)(μ-O)](BF4) (3) (L = PPh3, R = Ph, p-tol, p-ButC6H4) or [(PPh3)4Pt2(μ-O)(μ-NHR)](OTf) (L = PPh3, R = p-NO2C6H4) (3a). Deprotonation of the diamido complexes 2 (L2 = dppm, R = H, Ph, p-tol, NH2) with LiN(SiMe3)2 yields [(dppm-H)Pt(μ-NHR)]2 (4) (R = H, Ph, p-tol) or [(dppm-H)2Pt2(μ-NHNH2)2Li(THF)2]BF4 (5). Crystals of 4 (R = Ph) from CH2Cl2/ether are (183 K) orthorhombic (Pna21) with a = 38.272(2) Å, b = 9.2841(5) Å, c = 15.0099(7) Å, and Z = 4. The structure consists of two edge-shared square-planar Pt centers folded at the edge with syn-bridging amido groups and chelating dppm-H ligands. Crystals of 5·5THF from THF are (183 K) monoclinic (P21/n) with a = 17.669(5) Å, b = 31.884(3) Å, c = 14.686(4) Å, β = 105.03(1)°, and Z = 4. The structure of the cationic portion shows two edge-shared square-planar Pt centers folded at the edge with syn-bridging NHNH2 groups and chelating dppm-H ligands. The NHNH2 groups bridge the Pt centers through the NH portion. The NH2 portions coordinate to a Li(THF)2+ group in a “tweezers” fashion resulting in tetrahedral coordination about the Li atom. Further deprotonation of 4 with LiMe yields the anionic diimido complexes [(dppm-H)Pt(μ-NR)]2(Li)2 (6) (R = H, Ph, p-tol).

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